using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Security.Cryptography;

namespace Pay.Core.AlipayWap {
	/// <summary>
	/// 类名：RSAFromPkcs8
	/// 功能：RSA解密、签名、验签
	/// 详细：该类对Java生成的密钥进行解密和签名以及验签专用类，不需要修改
	/// 版本：2.0
	/// 修改日期：2011-05-10
	/// 说明：
	/// 以下代码只是为了方便商户测试而提供的样例代码，商户可以根据自己网站的需要，按照技术文档编写,并非一定要使用该代码。
	/// 该代码仅供学习和研究支付宝接口使用，只是提供一个参考。
	/// </summary>
	public sealed class RSAFromPkcs8 {
		/// <summary>
		/// 签名
		/// </summary>
		/// <param name="content">需要签名的内容</param>
		/// <param name="privateKey">私钥</param>
		/// <param name="input_charset">编码格式</param>
		/// <returns></returns>
		public static string sign(string content, string privateKey, string input_charset) {
			return RSASignCharSet(content, privateKey, input_charset);
		}

		public static string RSASignCharSet(string data, string privateKeyPem, string charset) {
			RSACryptoServiceProvider rsaCsp = LoadCertificateFile(privateKeyPem);
			byte[] dataBytes = null;
			if (string.IsNullOrEmpty(charset)) {
				dataBytes = Encoding.UTF8.GetBytes(data);
			} else {
				dataBytes = Encoding.GetEncoding(charset).GetBytes(data);
			}

			byte[] signatureBytes = rsaCsp.SignData(dataBytes, "SHA1");

			return Convert.ToBase64String(signatureBytes);
		}

		private static RSACryptoServiceProvider LoadCertificateFile(string filename) {
			using (FileStream fs = System.IO.File.OpenRead(filename)) {
				byte[] data = new byte[fs.Length];
				byte[] res = null;
				fs.Read(data, 0, data.Length);
				if (data[0] != 0x30) {
					res = GetPem("RSA PRIVATE KEY", data);
				}
				try {
					RSACryptoServiceProvider rsa = DecodeRSAPrivateKey(res);
					return rsa;
				} catch {
				}
				return null;
			}
		}

		private static byte[] GetPem(string type, byte[] data) {
			string pem = Encoding.UTF8.GetString(data);
			string header = String.Format("-----BEGIN {0}-----\\n", type);
			string footer = String.Format("-----END {0}-----", type);
			int start = pem.IndexOf(header) + header.Length;
			int end = pem.IndexOf(footer, start);
			string base64 = pem.Substring(start, (end - start));

			return Convert.FromBase64String(base64);
		}

		/// <summary>
		/// 验证签名
		/// </summary>
		/// <param name="content">需要验证的内容</param>
		/// <param name="signedString">签名结果</param>
		/// <param name="publicKey">公钥</param>
		/// <param name="input_charset">编码格式</param>
		/// <returns></returns>
		public static bool Verify(string content, string signedString, string publicKey, string input_charset) {
			bool result = false;

			Encoding code = Encoding.GetEncoding(input_charset);
			byte[] Data = code.GetBytes(content);
			byte[] data = Convert.FromBase64String(signedString);
			RSAParameters paraPub = ConvertFromPublicKey(publicKey);
			RSACryptoServiceProvider rsaPub = new RSACryptoServiceProvider();
			rsaPub.ImportParameters(paraPub);

			SHA1 sh = new SHA1CryptoServiceProvider();
			result = rsaPub.VerifyData(Data, sh, data);
			return result;
		}

		/// <summary>
		/// 用RSA解密
		/// </summary>
		/// <param name="resData">待解密字符串</param>
		/// <param name="privateKey">私钥</param>
		/// <param name="input_charset">编码格式</param>
		/// <returns>解密结果</returns>
		public static string decryptData(string resData, string privateKey, string input_charset) {
			byte[] DataToDecrypt = Convert.FromBase64String(resData);
			List<byte> result = new List<byte>();

			for (int j = 0; j < DataToDecrypt.Length / 128; j++) {
				byte[] buf = new byte[128];
				for (int i = 0; i < 128; i++) {
					buf[i] = DataToDecrypt[i + 128 * j];
				}
				result.AddRange(decrypt(buf, privateKey, input_charset));
			}
			byte[] source = result.ToArray();
			char[] asciiChars = new char[Encoding.GetEncoding(input_charset).GetCharCount(source, 0, source.Length)];
			Encoding.GetEncoding(input_charset).GetChars(source, 0, source.Length, asciiChars, 0);
			return new string(asciiChars);
		}

		private static byte[] decrypt(byte[] data, string privateKey, string input_charset) {
			RSACryptoServiceProvider rsa = DecodePemPrivateKey(privateKey);
			//SHA1 sh = new SHA1CryptoServiceProvider();
			return rsa.Decrypt(data, false);
		}

		/// <summary>
		/// 解析java生成的pem文件私钥
		/// </summary>
		/// <param name="pemstr"></param>
		/// <returns></returns>
		private static RSACryptoServiceProvider DecodePemPrivateKey(String pemstr) {
			byte[] pkcs8privatekey;
			pkcs8privatekey = Convert.FromBase64String(pemstr);
			if (pkcs8privatekey != null) {

				RSACryptoServiceProvider rsa = DecodePrivateKeyInfo(pkcs8privatekey);
				return rsa;
			} else
				return null;
		}

		private static RSACryptoServiceProvider DecodePrivateKeyInfo(byte[] pkcs8) {

			byte[] SeqOID = { 0x30, 0x0D, 0x06, 0x09, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x01, 0x01, 0x05, 0x00 };
			byte[] seq = new byte[15];

			MemoryStream mem = new MemoryStream(pkcs8);
			int lenstream = (int)mem.Length;
			BinaryReader binr = new BinaryReader(mem);    //wrap Memory Stream with BinaryReader for easy reading
			byte bt = 0;
			ushort twobytes = 0;

			try {

				twobytes = binr.ReadUInt16();
				if (twobytes == 0x8130) //data read as little endian order (actual data order for Sequence is 30 81)
					binr.ReadByte();    //advance 1 byte
				else if (twobytes == 0x8230)
					binr.ReadInt16();   //advance 2 bytes
				else
					return null;


				bt = binr.ReadByte();
				if (bt != 0x02)
					return null;

				twobytes = binr.ReadUInt16();

				if (twobytes != 0x0001)
					return null;

				seq = binr.ReadBytes(15);       //read the Sequence OID
				if (!CompareBytearrays(seq, SeqOID))    //make sure Sequence for OID is correct
					return null;

				bt = binr.ReadByte();
				if (bt != 0x04) //expect an Octet string 
					return null;

				bt = binr.ReadByte();       //read next byte, or next 2 bytes is  0x81 or 0x82; otherwise bt is the byte count
				if (bt == 0x81)
					binr.ReadByte();
				else
					if (bt == 0x82)
					binr.ReadUInt16();
				//------ at this stage, the remaining sequence should be the RSA private key

				byte[] rsaprivkey = binr.ReadBytes((int)(lenstream - mem.Position));
				RSACryptoServiceProvider rsacsp = DecodeRSAPrivateKey(rsaprivkey);
				return rsacsp;
			} catch (Exception) {
				return null;
			} finally { binr.Close(); }

		}


		private static bool CompareBytearrays(byte[] a, byte[] b) {
			if (a.Length != b.Length)
				return false;
			int i = 0;
			foreach (byte c in a) {
				if (c != b[i])
					return false;
				i++;
			}
			return true;
		}

		private static RSACryptoServiceProvider DecodeRSAPrivateKey(byte[] privkey) {
			byte[] MODULUS, E, D, P, Q, DP, DQ, IQ;

			// ---------  Set up stream to decode the asn.1 encoded RSA private key  ------
			MemoryStream mem = new MemoryStream(privkey);
			BinaryReader binr = new BinaryReader(mem);    //wrap Memory Stream with BinaryReader for easy reading
			byte bt = 0;
			ushort twobytes = 0;
			int elems = 0;
			try {
				twobytes = binr.ReadUInt16();
				if (twobytes == 0x8130) //data read as little endian order (actual data order for Sequence is 30 81)
					binr.ReadByte();    //advance 1 byte
				else if (twobytes == 0x8230)
					binr.ReadInt16();   //advance 2 bytes
				else
					return null;

				twobytes = binr.ReadUInt16();
				if (twobytes != 0x0102) //version number
					return null;
				bt = binr.ReadByte();
				if (bt != 0x00)
					return null;


				//------  all private key components are Integer sequences ----
				elems = GetIntegerSize(binr);
				MODULUS = binr.ReadBytes(elems);

				elems = GetIntegerSize(binr);
				E = binr.ReadBytes(elems);

				elems = GetIntegerSize(binr);
				D = binr.ReadBytes(elems);

				elems = GetIntegerSize(binr);
				P = binr.ReadBytes(elems);

				elems = GetIntegerSize(binr);
				Q = binr.ReadBytes(elems);

				elems = GetIntegerSize(binr);
				DP = binr.ReadBytes(elems);

				elems = GetIntegerSize(binr);
				DQ = binr.ReadBytes(elems);

				elems = GetIntegerSize(binr);
				IQ = binr.ReadBytes(elems);

				// ------- create RSACryptoServiceProvider instance and initialize with public key -----
				RSACryptoServiceProvider RSA = new RSACryptoServiceProvider();
				RSAParameters RSAparams = new RSAParameters();
				RSAparams.Modulus = MODULUS;
				RSAparams.Exponent = E;
				RSAparams.D = D;
				RSAparams.P = P;
				RSAparams.Q = Q;
				RSAparams.DP = DP;
				RSAparams.DQ = DQ;
				RSAparams.InverseQ = IQ;
				RSA.ImportParameters(RSAparams);
				return RSA;
			} catch (Exception) {
				return null;
			} finally { binr.Close(); }
		}

		private static int GetIntegerSize(BinaryReader binr) {
			byte bt = 0;
			byte lowbyte = 0x00;
			byte highbyte = 0x00;
			int count = 0;
			bt = binr.ReadByte();
			if (bt != 0x02)     //expect integer
				return 0;
			bt = binr.ReadByte();

			if (bt == 0x81)
				count = binr.ReadByte();    // data size in next byte
			else
				if (bt == 0x82) {
				highbyte = binr.ReadByte(); // data size in next 2 bytes
				lowbyte = binr.ReadByte();
				byte[] modint = { lowbyte, highbyte, 0x00, 0x00 };
				count = BitConverter.ToInt32(modint, 0);
			} else {
				count = bt;     // we already have the data size
			}



			while (binr.ReadByte() == 0x00) {   //remove high order zeros in data
				count -= 1;
			}
			binr.BaseStream.Seek(-1, SeekOrigin.Current);       //last ReadByte wasn't a removed zero, so back up a byte
			return count;
		}

		#region 解析.net 生成的Pem
		private static RSAParameters ConvertFromPublicKey(string pemFileConent) {

			byte[] keyData = Convert.FromBase64String(pemFileConent);
			if (keyData.Length < 162) {
				throw new ArgumentException("pem file content is incorrect.");
			}
			byte[] pemModulus = new byte[128];
			byte[] pemPublicExponent = new byte[3];
			Array.Copy(keyData, 29, pemModulus, 0, 128);
			Array.Copy(keyData, 159, pemPublicExponent, 0, 3);
			RSAParameters para = new RSAParameters();
			para.Modulus = pemModulus;
			para.Exponent = pemPublicExponent;
			return para;
		}

		private static RSAParameters ConvertFromPrivateKey(string pemFileConent) {
			byte[] keyData = Convert.FromBase64String(pemFileConent);
			if (keyData.Length < 609) {
				throw new ArgumentException("pem file content is incorrect.");
			}

			int index = 11;
			byte[] pemModulus = new byte[128];
			Array.Copy(keyData, index, pemModulus, 0, 128);

			index += 128;
			index += 2;//141
			byte[] pemPublicExponent = new byte[3];
			Array.Copy(keyData, index, pemPublicExponent, 0, 3);

			index += 3;
			index += 4;//148
			byte[] pemPrivateExponent = new byte[128];
			Array.Copy(keyData, index, pemPrivateExponent, 0, 128);

			index += 128;
			index += ((int)keyData[index + 1] == 64 ? 2 : 3);//279
			byte[] pemPrime1 = new byte[64];
			Array.Copy(keyData, index, pemPrime1, 0, 64);

			index += 64;
			index += ((int)keyData[index + 1] == 64 ? 2 : 3);//346
			byte[] pemPrime2 = new byte[64];
			Array.Copy(keyData, index, pemPrime2, 0, 64);

			index += 64;
			index += ((int)keyData[index + 1] == 64 ? 2 : 3);//412/413
			byte[] pemExponent1 = new byte[64];
			Array.Copy(keyData, index, pemExponent1, 0, 64);

			index += 64;
			index += ((int)keyData[index + 1] == 64 ? 2 : 3);//479/480
			byte[] pemExponent2 = new byte[64];
			Array.Copy(keyData, index, pemExponent2, 0, 64);

			index += 64;
			index += ((int)keyData[index + 1] == 64 ? 2 : 3);//545/546
			byte[] pemCoefficient = new byte[64];
			Array.Copy(keyData, index, pemCoefficient, 0, 64);

			RSAParameters para = new RSAParameters();
			para.Modulus = pemModulus;
			para.Exponent = pemPublicExponent;
			para.D = pemPrivateExponent;
			para.P = pemPrime1;
			para.Q = pemPrime2;
			para.DP = pemExponent1;
			para.DQ = pemExponent2;
			para.InverseQ = pemCoefficient;
			return para;
		}
		#endregion

	}
}
